An International Conference on the Surgical Therapy of Epilepsy is proposed to be held at the Miramar Hotel in Santa Monica February 20-22, 1986. This year will be the Centennial Anniversary of Horsley's Classic paper on surgical resection of an epileptic lesion which marked the beginning of the modern era of surgical therapy for epilepsy. Despite this one hundred year history, it is only relatively recently that surgery has become accepted as a serious alternative mode for treating epilepsy, and even today there are those who doubt its value. Furthermore, among advocates of surgical therapy, there are no agreed upon standard diagnostic approaches, or surgical procedures, and widely divergent views are held by practitioners in different centers throughout the world. There has never been a national, or international conference on this subject to attempt to discuss and resolve these issues. In the past decade in particular, it has become apparent that great numbers of patients with medically refractory seizures could benefit, or become seizure free, with modern surgical treatment. As many as 250,000 epileptic patients in the U.S. alone might be considered candidates for surgical therapy, while barely 200 of these procedures are performed in the U.S. annually. Consequently, centers that offer epilepsy surgery are faced with long waiting lists and are expanding, while new centers are rapidly developing in the U.S. and abroad. There is now a pressing need to evaluate and organize recent progress in the field of surgery for epilepsy, and to insure that efforts during this period of growth are directed to provide the most effective patient care and the greatest opportunities for research on the human brain. A formal conference is proposed to: 1) describe the current diagnostic approaches in surgical procedures that have become standard at the major epilepsy centers in the world, in order to define areas of agreement and controversy; 2) identify those aspsects of the presurgical evaluation, surgical treatment, and postsurgical follow-up where controversy can be resolved or improvements can be made by careful scientific scrutiny, in order to design collaborative clinical investigative approaches that can be undertaken at multiple centers; 3) demonstrate how epilepsy surgery programs provide opportunity for basic research on normal and abnormal human brain function, in order to encourage basic and clinical neuroscientist to work together to take maximum advantage of these unique facilities; and 4) publish a comprehensive and well referenced text that details the state of the art 100 years after Horsley's paper began the modern era of epilepsy surgery.